We will carry out experiments on the circadian rhythm of activity in the eye of Aplysia and in locomotor behavior. Aside from pilot projects we will study the following questions: (1) Are there photoreceptors in the CNS of Aplysia which can mediate entrainment of the eye rhythm? (2) Is there an oscillator in the CNS which is coupled to the oscillator in the eye? (3) Are th circadian oscillators in the two eyes coupled to each other and if so what is the nature of the coupling signal? (4) Can extraocular photoreceptors entrain extraocular oscillators? We also hope to complete three manuscripts based on data already collected: (1) The role of the optic nerve in mediating the action of the eye on the circadian locomotor rhythm. (2) The action of various lighttimes and various daylengths on the phase of the locomotor rhythm in intact and eyeless Aplysia. (3) The action of LD, DD and temperature cycles on activity of the eyes and neuron R15 maintained in long term organ culture. BIBLIOGRAPHIC REFERENCE: Lickey, M.E., Wozniak, J.A., Block, G.D., Hudson, D.J., and Augter, G.K. The consequences of eye removal for the circadian rhythm of behavioral activity in Aplysia. J. Comp. Physiol. A, 1977. In press.